A capacitance sensor configured to detect positions or actions of detected objects by a change in capacitance is known. The capacitance sensor includes one or more electrodes for detection. When the detected object approaches the electrode for detection, a capacitance value generated between an electrode and an electrode, or between an electrode and the ground varies. The capacitance sensor is an apparatus configured to detect actions of the detected objects by measuring the change in capacitance value as an electric signal.
JP 2006-213206 A discloses a vehicle window sensor configured to detect variations in capacitance between two electrodes including a sensor electrode installed on a window glass of a vehicle as one electrode, and a vehicle body as the other electrode.
The vehicle window sensor disclosed in JP 2006-213206 A is configured to detect the capacitance between the electrode on the window glass and the vehicle body and thus has a wide detecting area. In the case where the vehicle window sensor is used as an operation detecting unit, the vehicle window sensor has a potential to detect operation erroneously even though a user does not perform operation such as the case where a person passes near by the vehicle at the time of parking.